Search for Neutrino-less Double Beta Decay of ${}^{64}$Zn and ${}^{70}$Zn with CUPID-0

Abstract

CUPID-0 is the first pilot experiment of CUPID, a next-generation project searching for neutrino-less double beta decay. In its first scientific run, CUPID-0 operated 26 ZnSe cryogenic calorimeters coupled to light detectors in the underground Laboratori Nazionali del Gran Sasso. In this work, we analyzed a ZnSe exposure of 11.34 kg$\times$yr to search for the neutrino-less double beta decay of ${}^{70}$Zn and for the neutrino-less positron-emitting electron capture of ${}^{64}$Zn. We found no evidence for these decays and set 90$\%$ credible interval limits of ${\mathrm{T}}_{1/2}^{0\hat{I}½{\hat{I}}^2{\hat{I}}^2}{(}^{70}\mathrm{Zn})>1.6\times 10^{21}$ yr and ${\mathrm{T}}_{1/2}^{0\hat{I}½EC{\hat{I}}^2+}{(}^{64}\mathrm{Zn})>1.2\times 10^{22}$ yr, surpassing by almost two orders of magnitude the previous experimental results